The Trey Edward Shults post-apocalyptic drama It Comes At Night explained, albeit subtly, the many themes at play in its story of a family trying to survive in a world ravaged by an unexplained virus. This mysterious virus kills off a large swathe of the population, and a family (Paul, Sarah, and teenage son Travis) has been surviving in a ramshackle cabin in the woods cut off from fellow survivors — that is until Will (Christopher Abbott) breaks in. After making sure he’s virus-free, Paul (Joel Edgerton) reluctantly allows Will and his family inside. Unfortunately, the living arrangements turn violently sour by the time It Comes At Night's ending arrives.
https://screenrant.com/it-comes-at-night-movie-ending-explained/